This application claims the benefit of Japanese Patent Application No. 2003-397006, filed Nov. 27, 2003.
1. Field of the Invention
The present invention relates to a carburetor for supplying fuel to a general-purpose, internal combustion engine used as a power source of a portable operating machine or the like, and more particularly, to a carburetor with a manual choke mechanism.
2. Description of Related Art
It is known to improve an engine's starting properties when temperatures are low, by placing a choke valve in an inlet of an intake passage of a carburetor and opening a throttle valve slightly from an idle position, as well as fully closing the choke valve. The carburetor for the general-purpose, internal combustion engine employs a manual choke mechanism which may be placed in a confined space and fabricated at a low cost with a reduced number of parts.
The choke valve in known manual choke mechanisms is of a fixed type, in which the choke valve is mounted to a choke valve shaft crossing a center axis of the intake passage, and is started by the delicate operation of changing the choke valve from a full close state to a full open state by the manual operation of the choke valve by the driver, and changing the throttle valve at an appropriate time by operation of the throttle valve by the driver. Accordingly, for example, as described in Japanese Utility Model Publication No. 35-4305, Japanese Unexamined Patent Publication No. 49-109738 and “Theory and Practice of Carburetor” written by Takashi Yoshida, issued by Railroad Japan Company, in 1980, it is possible to employ a semiautomatic choke mechanism structured, such that the choke valve and the throttle valve are interlocked by a link mechanism to the manual choke mechanism, and the throttle valve is opened slightly from the idle position when the choke valve is fully closed. In this case, it is possible to start the engine without this delicate operation.
However, when fully closing the choke valve by manual operation prior to the manual choke mechanism, the operating force may be applied at least until the engine is completely fired. In particular, in the manual choke mechanism, to which the semiautomatic choke mechanism is applied, there is a danger that the choke valve and the throttle valve may become unstable by releasing either or both of the valves immediately when the valves are fully closed, whereby it may be impossible to securely hold the choke and throttle valves at their respective fully closed position and slightly open position, so as to securely start the engine.